The I2C Touch Sensor is based on FreeScale MPR121, to feel the touch or proximity of human being fingers. This sensor include 2 parts: one Touch Sensor controller, and 4 finger feelers. Insert the connectors of feelers into base of Sensor controller, you can begin your touch controlling. 

MPR121: The MPR121 is a capacitive touch sensor controller,features internal intelligence, include an hardware configurable I2C address, an expended filtering system with debounce, and completely independent electrodes with auto-configuration built in . 

Touch Sensor feeler: The Touch Sensor feelers, which was 4 included in Touch Sensor module,can be set in any place you like, to feel your finger's touch or proximity. Notice it must not get in touch with any conductive material.